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AppGameKit Classic Chat / shooting a cannon ball

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shadey
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Posted: 4th Feb 2013 11:38
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can someone give me a simple example of shooting a cannon ball out of a cannon at the given cannon angle (that is adjustable by buttons) using physics for the ball of course! been trying all weekend but cannot work it out myself... Thanks!

Hail to the king, baby!
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ProfVersaggi
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Posted: 4th Feb 2013 12:55
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I can give you an example of that but it'll be a battleship turret and projectiles if that's acceptable ... I've worked on that thorny problem for a while and have some experience solving it ...

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Markus
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Posted: 4th Feb 2013 13:04
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i am not at home but its easy.
the angle give you the speed with sin/cos in x and y direction.
the weight and gravity pull your ball down over time.

angle#=45 //degree
speed#=???

vx#=cos(angle#)*speed#
vy#=sin(angle#)*speed#

SetSpritePhysicsImpulse()

http://www.appgamekit.com/documentation/Reference/Sprite.htm
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shadey
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Posted: 4th Feb 2013 13:47 Edited at: 4th Feb 2013 13:57
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thank you marcus, this explains fully where I was going wrong! I see how it works now. The only thing is though that on different angles it does not travel as far with the same speed, so if I set the angle at 90 for instance, it would reach the top of the screen with a speed of say 4, but change the angle and of course it doesnt travel as far, if I want the user to simply be able to adjust the power of the shot, which I guess is just the speed? then how do I overcome this ?!

Hail to the king, baby!
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ProfVersaggi
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Posted: 4th Feb 2013 14:18
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Be sure to set your gravity to Zero ...

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Markus
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Posted: 5th Feb 2013 12:32 Edited at: 5th Feb 2013 12:38
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if you shoot up it can't goto the right without wind.
but you can limit the angle that it must move a little bit to the left or right.
also importent is the physic scale because the default
was set up for 100% width = 100 meters.
you can simulate wind by add acceleration at x.

alternative without physics you can use start/end coordinates
and the angle/flight path is the result of a formula.
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